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SAB82520高级串行通信控制器以两条独立的、数据传送率高达4Mbps的全双工HDLC(高级数据链路控制)通道为特色。这种控制器采用X.25 LAPB/LAPD协议(链路访问协议B和D)。在自动方式上,该控制器完成面向ISO HDLC通信协议层1的功能和某些层2的功能。例如,它判定层2控制字段以完成通信规程的信号交换。但象协议错误需要的连接建立和恢复这样的功能则要求CPU支持才行。在透明方式上,该控制器向CPU直接传送数据字段和层2的标头,并交给CPU以控制通信规程。收、发分开的FIFO缓冲器的容量均为64字节,它们可作为中断传送的32字节大容量缓冲器来操作,并允许处理器读写其中一个缓冲器,而另一个则可以接收和发送数据。这种用CMOS制造的28腿器件在时钟速率为4MHz时,只使用一个5V电源,其工作电流为5mA.
The SAB82520 advanced serial communications controller features two independent full-duplex HDLC (Advanced Data Link Control) channels with data rates up to 4 Mbps. This controller uses the X.25 LAPB / LAPD protocol (link access protocols B and D). In automatic mode, the controller performs the functions for layer 1 of ISO HDLC communication protocol and the functions of some layers 2. For example, it determines that layer 2 controls the fields to complete handshaking of communication protocols. But like protocol errors need to connect and restore such a feature requires CPU support Caixing. In a transparent manner, the controller sends the data field and the header of layer 2 directly to the CPU and hands it over to the CPU to control the communication procedures. Both the receive and transmit FIFO buffers are 64 bytes in size and operate as a 32-byte bulk buffer for interrupt transfers and allow the processor to read and write to one of the buffers while the other can receive and send data. This 28-leg device fabricated in CMOS uses only a 5V supply at a clock rate of 4 MHz and operates at 5 mA.